1. Field of the Invention
The present disclosure generally relates to wireless communications and more particularly relates to systems and methods for improving the reliability of multicast/broadcast traffic from an access point.
2. Background Information
Among other things, FIG. 1 illustrates a typical network configuration for communicating data between stations via an access point in a wireless local area network (WLAN) or 802.11-based network. As illustrated in the non-limiting example of FIG. 1, a network 140 may be coupled to access point 130. In some embodiments, the network 140 may be the Internet, for example. Access point 130 can be configured to provide wireless communications to various wireless devices or stations 110, 120, 124. Depending on the particular configuration, the stations 110, 120, 124 may be a personal computer (PC), a laptop computer, a mobile phone, a personal digital assistant (PDA), and/or other device configured for wirelessly sending and/or receiving data. Furthermore, the access points 130 may be configured to provide a variety of wireless communications services, including but not limited to: Wireless Fidelity (WIFI) services, Worldwide Interoperability for Microwave Access (WiMAX) services, and wireless session initiation protocol (SIP) services. Furthermore, the stations 110, 120, 124 may be configured for WIFI communications (including, but not limited to 802.11, 802.11b, 802.11a/b, 802.11g, and/or 802.11n).
Access point 130 can transmit to a single station such as station 110 which is known as a unicast transmission. Access point 130 can also transmit to all stations which is known as a broadcast transmission. Access point 130 can also transmit to a subset of all stations which is known as multicast transmissions.
As illustrated in FIG. 2, access point 130 transmits a beacon frame at a target beacon transmission time (TBTT). The beacon frame comprises a beacon interval which indicates the period of time between beacons. In the timeline shown here, beacon frames 202, 204, 206, 208, and 210 represent five beacon frames transmitted by the access point. The frequency of the beacon frames is represented by the period equal to the beacon interval. Each of the beacon frames in the example contains a traffic indication map (TIM) element. Specifically, beacon frames 202, 204, 206, and 210 contain TIM elements 212, 214, 216, 218 and 220, respectively. Periodically, the TIM element in the beacon frame is a delivery traffic indication map (DTIM), which indicates after the beacon frame the access point will transmit buffered multicast or broadcast data. This beacon frame is sometimes referred to as a DTIM beacon frame.
In the past, broadcast/multicast (BM) traffic in wireless network was generally used to control traffic. Under such context, BM frames were infrequent and short. Also, BM frames were transmitted at a basic rate due to the requirement that all associated stations should be able to receive it. In addition BM traffic was not reliable because it is not acknowledged. However, in today's networking environment there is a large market segment for delivery of streaming media such as audio and video streams using multicast streams. To improve the quality of streaming video and audio multicast, reliability needs to be improved and the throughput rate of the multicast data transmission needs to be higher. Accordingly, various needs exist in the industry to address the aforementioned deficiencies and inadequacies.